Kevin great info.
The ultra low sulfur fuel? Could it be hurting you by a full 7/10ths?
Another question for you heavy haulin stacker bunch.
What is the tongue weight, empty trlr.?
Seems like individual fuel mileages are all over the place although Jack did not say at what speed he clocked in that 4.1mpg.
Kevin the milages you have noted are more in line to what they should be for pulling that stacker. You should get about the same as your KW does mabye a little less aka automatic trans. and flat nose.
I think a used bus with mileage of 7+ with some sort of decent proof is valuable to potential buyers who will be frequent users. Especially now when it looks like the newer stuff isin't hitting that mark anymore.
Kevin you said your 99 got 7.2 at 68? Do you remember what it got at 62.5.